Flare fittings are a type of compression fitting used with metal tubing, usually soft steel, ductile (soft) copper and aluminum, though other materials are also used.  Tube flaring is a type of forging operation and is usually a cold working procedure.  During assembly, a flare nut is used to secure the flared tubing’s tapered end to the also tapered fitting, producing a pressure-resistant, leak-tight seal. Flared connections offer a high degree of long-term reliability and for this reason are often used in mission-critical and inaccessible locations.

The tool used to flare tubing consists of a die that grips the tube and either a mandrel or rolling cone is forced into the end of the tube to form the flare by cold working.

The most common flare fitting standards in use today are the 45° SAE flare, the 37° JIC flare, and the 37° AN flare.